A Heat Exchanger and Uses Thereof

ABSTRACT

A heat exchanger unit having a top and a bottom, the heat exchanger comprising a plurality of fins spaced apart from each other and having a predetermined length, thickness and height, with application for use with a photovoltaic solar panel.

FIELD OF THE INVENTION

The invention relates to a heat exchanger and uses thereof.Specifically, the invention relates to a heat exchanger with apredetermined geometry that is suitable for use with devices such asphotovoltaic solar panels, and other devices requiring heating orcooling.

BACKGROUND TO THE INVENTION

Modern, silicon-based photovoltaic solar panels can produce 20%efficiencies when tested under standard conditions of 1000 W/m² at 25°C. and are rated to last for 20 years. That is, for a given power ofsunlight incident on the panel surface, 20% of this is converted toelectricity. The other 80% is reflected or generates heat leading tosignificant temperature rises in the panel. In areas with high solarirradiance, and high air temperature, the panel temperature can exceed100° C. The immediate effect of this is to reduce panel efficiency dueto temperature dependencies in the underlying physics, but also toaccelerate natural degradation mechanisms which depend exponentially ontemperature. In general, efficiency decreases by 0.5% for every degreethe panel is above 25° C. The panel lifetime depends on the averageannual panel temperature, and halves for every 10° C. above 25° C. Largetemperature swings such as those seen in desert climates can alsosignificantly accelerate panel degradation.

The long-term degradation of solar photovoltaic (PV) cells is well knownin the industry and panel manufactures provide warrantees which includethis degradation. This degradation rate can be up to 2% in the first twoyears, and then reduces approximately linearly at a slower rate. Therate of efficiency loss is known as the power coefficient β and formodern silicon solar cell designs is between 0.3-0.6% per annum or moredepending on the cell technology and panel geometry. Ideally, after theagreed term ˜20 years, the panel should still be producing electricityat 80% of its rated efficiency. To achieve this the power coefficientshould be less than 1%.

Twenty years is an extremely long time for a product to remain inservice, and critical failure can occur due to a number of differenteffects, including but not limited to, water ingress, physical damage,sand abrasion, cementation, frame corrosion, back panel degradation,delamination, overheating, shading effects, short circuits, opencircuits, damage of intra and inter cell connections. As such, extremelyhigh-quality starting materials and manufacturing process must be usedto guarantee efficiency over operational lifetime. Some companies focuson longevity of various components of the solar cell and solar panelconstruction. They produce conductive inks, adhesives and solar backsheets with a focus on quality for extreme conditions. Elevatedoperating temperature has particularly adverse effects in arid,semi-arid and tropical environments where cell degradation can besignificantly accelerated.

Previously proposed cooling technologies include natural air convection,forced air convection, natural fluid convection, forced fluidconvection, spray cooling, radiative cooling, active cooling, andthermoelectric cooling. These cooling mechanisms come at additionalenergy or capital cost, or require large amounts of water, which isoften scarce in arid areas in which solar is deployed.

WO 2018/117337 describes a solar cell cooling device that utilises bothnatural convective air flow and forced convective air flow through aseries of spaced-apart fins having an air inlet and an air outlet. Theproblem with this device is that narrowing the space of the channel willincrease airflow, but this is not an effective approach when usingnatural convection, as the geometry of the device will result inincreased viscous drag and reduce the airflow rate. These fin structurecreates closed channels which will not benefit from mixing due to windbased forced convection.

CN204597884 describes a photovoltaic module junction box heat exchanger.The heat exchanger is made from aluminium, which is adhered to a heatconductive graphite paste. This patent refers to dissipating excess heatat the junction box only and does not relate to cooling the entire backsection of a solar panel.

WO 2010/080204 describes a solar receiver (a base plate having a firstsurface and a second surface, a plurality of solar cells positioned overand supported by the first surface of the base plate) with a heatexchanger. The heat exchanger can be made from aluminium or copper andcomprises a plurality of fins formed or fabricated from one continuousroll or sheet of material and bent to form a serpentine configuration.This heat exchanger refers to the application of concentratedphotovoltaics (CPV), which is quite different to the PV geometry used instandard PV panels. The application uses standard folded fin designs andconstruction techniques.

US 2006/137733 shows a heat exchanger applied to a PV module which isconstructed by continuously folding a single sheet of material. The finsdescribed are continuous along the length of the panel.

US 2010/154788 applies conventional folded heat exchanger designsincluding continuous and wavey fins to a concentrated solar collector,but which could not benefit from convective mixing due to wind. Due tothe concentrated nature of the heat source, fin density will be highermeaning that the optimum fin spacing will be closer than for aconventional solar panel.

JP 2016 015385 appears to show continuous fins formed from a thin metalsheet with polymer backing. The heat exchanger is formed by continuouslyfolding a single sheet of material, which results in a lot of materialusage.

It is an object of the present invention to overcome at least one of theabove-mentioned problems.

SUMMARY OF THE INVENTION

Due to the relatively low heat source density expected in photovoltaicsolar panels (<2000 W/m²), and the large thermal resistance of the backplate, even a very low efficiency heat exchanger could have asignificant effect on the steady state temperature. Previous works havetaken passive natural convection heat exchanger designs from integratedelectronics, and automotive applications, where relatively large heatsource densities must be dissipated. They concluded that passive heatexchanging of photovoltaic solar panels was not cost effective due tothe quantity of aluminium required. One of the aims here is to showthat, with the lower heat source density in solar panels, the inventorscan use much less aluminium material, or even change material topolymers, or carbon-based materials for example. This will allow forbetter heat exchanger design and achieve a significant reduction insteady state operating temperature in a cost-effective manner. Theinventors have identified that that conversion efficiency and panellifetime can be significantly reduced when panels are deployed on sitesdepending on local climate. The efficiency and lifetime of photovoltaicsolar panels are key parameters which directly affect the cost ofphotovoltaic solar panels. This determines its competitiveness and sharein the energy mix, and ultimately the monetary and carbon footprint costto each consumer.

The efficiency drop with increasing temperature is due to thetemperature dependence of the bandgap of the semiconductor material.This temperature dependence is accounted for in the diode equation,which describes the electrical performance of the photovoltaic cell.Temperature dependence of efficiency is an important property regardlessof the underlying solar cell technology and the invention describedherein could be used with many photovoltaic technologies including butnot limited to monocrystalline, polycrystalline and amorphous silicon,thin film cells, cadmium telluride, gallium arsenide, copper indiumgallium selenide (CIGs), organic solar cells, perovskite solar cells,multijunction cells, dye sensitised solar cells, quantum dot solarcells, plasmonic and nanocrystal sensitised solar cells. This technologycould also be used to improve the performance of electrochemical cellsor fuel cells or thermoelectric generators.

In one aspect, there is provided a heat exchanger, the heat exchangercomprising a plurality of fins spaced apart from each other and each finhaving a predetermined length (L_(fin)), thickness (t_(fin)) and height(h_(fin)); and wherein each fin of the plurality of fins has apredetermined shape and is attached individually to a plate. The heatexchanger is suitable for use with a heat source.

In one aspect, the plurality of fins are composed of the same material,a composite of the same material, or a composite of different material.

In one aspect, there is provided a heat exchanger for use with aphotovoltaic solar panel unit having a top and a bottom, the heatexchanger comprising a plurality of fins spaced apart from each otherand each fin of the plurality of fins having a predetermined length(L_(fin)), thickness (t_(fin)) and height (h_(fin)), wherein theplurality of fins are formed from a single sheet of material and whereinan aperture having a predetermined width (W_(A)) and a predeterminedlength (L_(A)) is generated in the single sheet of material between eachof the plurality of fins.

In one aspect, there is provided a heat exchanger for use with aphotovoltaic solar panel unit having a top and a bottom, the heatexchanger comprising a plurality of fins spaced apart from each otherand each fin having a predetermined length (L_(fin)), thickness(t_(fin)) and height (h_(fin)); wherein the optimum fin spacing isbetween about 1 mm and about 50 mm. That is, between about 1, 2, 3, 4,5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17 18, 19, 20, 21, 22, 23,24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 27, 38, 39, 40, 41,42, 43, 44, 45, 46, 47, 48, 49 and 50 mm, and any value individuallymentioned here.

In one aspect, there is provided a heat exchanger comprising a pluralityof fins spaced apart from each other and having a predetermined length(L_(fin)), thickness (t_(fin)) and height (h_(fin)); wherein theplurality of fins are formed from a single sheet of material and whereinwhere each fin of the plurality of fins are formed, an aperture having apredetermined width (W_(A)) and a predetermined length (L_(A)) isgenerated in the single sheet of material separating each fin of theplurality of fins. Ideally, the optimum fin spacing (S) is between about1 mm and about 50 mm. That is, between about 1, 2, 3, 4, 5, 6, 7, 8, 9,10, 11, 12, 13, 14, 15, 16, 17 18, 19, 20, 21, 22, 23, 24, 25, 26, 27,28, 29, 30, 31, 32, 33, 34, 35, 36, 27, 38, 39, 40, 41, 42, 43, 44, 45,46, 47, 48, 49 and 50 mm, and any value individually mentioned here.

In one aspect, the plurality of fins have on open configuration throughthe heat exchanger.

In one aspect, the plurality of fins are segmented into distinctsections.

In one aspect, the plurality of fins are arranged in a colinear or anoffset manner relative to each other.

In one aspect, fin spacing, fin height or fin thickness change as afunction of position on the single sheet of material.

In one aspect, the height of the plurality of fins increases in thedirection towards the top of the solar panel unit.

In one aspect, the fins have a thickness (t_(fin)) of between about0.001 mm to about 5 mm. That is, between about 0.001, 0.002, 0.003,0.004, 0.005, 0.006, 0.007, 0.008, 0.009, 0.010, 0.015, 0.020, 0.025,0.030, 0.035, 0.040, 0.045, 0.050, 0.055, 0.060, 0.065 0.070, 0.075,0.080, 0.085, 0.090, 0.095, 0.100 mm, 0.150 mm, 0.200 mm, 0.250 mm,0.300 mm, 0.350 mm, 0.400 mm, 0.450 mm, 0.500 mm, 0.550 mm, 0.600 mm,0.650 mm, 0.700 mm, 0.750 mm, 0.800 mm, 0.850 mm, 0.900 mm, 0.950 mm,1.000 mm, 1.1 mm, 1.2 mm, 1.3 mm, 1.4 mm, 1.5 mm, 1.6 mm, 1.7 mm, 1.8mm, 1.9 mm, 2.0 mm, 2.1 mm, 2.2 mm, 2.3 mm, 2.4 mm, 2.5 mm, 2.6 mm, 2.7mm, 2.8 mm, 2.9 mm, 3.0 mm, 3.1 mm, 3.2 mm, 3.3 mm, 3.4 mm, 3.5 mm, 3.6mm, 3.7 mm, 3.8 mm, 3.9 mm, 4.0 mm, 4.1 mm, 4.2 mm, 4.3 mm, 4.4 mm, 4.5mm, 4.6 mm, 4.7 mm, 4.8 mm, 4.9 mm, and 5.0 mm, and any valueindividually mentioned here.

In one aspect, the fins have a height (h_(fin)) at the bottom of thephotovoltaic solar panel unit of between about 0.5 cm to about 10 cm.That is, between about 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, 5.0,5.5, 6.0, 6.5, 7.0, 7.5, 8.0, 8.5, 9.0, 9.5 and 10 cm, and any valueindividually mentioned here.

In one aspect, the fins have a length of between about 10 mm to about1500 mm. That is, between about 10, 15, 20, 25, 30, 35, 40, 45, 50, 55,60, 65, 70, 75, 80, 85, 90, 95, 100, 150, 200, 250, 300, 350, 400, 450,500, 550, 600, 650, 700, 750, 800, 850, 900, 950, 1000, 1050, 1100,1150, 1200, 1250, 1300, 1350, 1400, 1450, and 1500 mm, and any valueindividually mentioned here.

In one aspect, the fins may be segmented and have a length (L_(fin)) ofbetween about 10 mm to about 1500 mm. That is, between about 10, 15, 20,25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100, 150,200, 250, 300, 350, 400, 450, 500, 550, 600, 650, 700, 750, 800, 850,900, 950, 1000, 1050, 1100, 1150, 1200, 1250, 1300, 1350, 1400, 1450,and 1500 mm, and any value individually mentioned here.

In one aspect, the spacing of the fins (S) is between about 0.5 cm toabout 5 cm. That is, between about 0.5, 0.75, 1.0, 1.25, 1.5, 1.75, 2.0,2.25, 2.5, 2.75, 3.0, 3.25, 3.5, 3.75, 4.0, 4.25, 4.5, 4.75, and 5.0 cm,and any value individually mentioned here.

In one aspect an interruption length (L_(int)) may be required ofbetween about 1 mm and about 50 mm. That is, between about 1, 2, 3, 4,5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17 18, 19, 20, 21, 22, 23,24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 27, 38, 39, 40, 41,42, 43, 44, 45, 46, 47, 48, 49 and 50 mm, and any value individuallymentioned here. The interruption length can increase air mixing in theheat exchanger.

In one aspect, the fins are composed of thermally conductive sheets orfilms selected from the group comprising metallic film, a carbon-basedfilm, or polymer films doped with conductive particles or a combinationthereof. Preferably, the metallic films are selected from filmscomprising aluminium, copper, stainless steel, tungsten, titanium, orcombinations thereof. Preferably, the carbon-based films are selectedfrom films comprising graphite, pyrolytic graphite, synthetic graphite,graphene or carbon nanotubes, expanded graphite, graphite composites,carbon black, diamond, or combinations thereof. Preferably, theconductive particles in the polymer films are selected from a diamond,carbon, transition metal nitrides such as AlN, transition metal oxidessuch as AlO₃, ceramics such as Si₃N₄, BN or SiC or combinations thereof.

In one aspect, the plurality of fins are flexible.

In one aspect, the plurality of fins are coated with an epoxy, acopolymer or a polymer. Preferably, the polymer or copolymer is selectedfrom an elastomer, a thermoplastic, a thermoset, a biopolymer, or acombination thereof.

In one aspect, the polymer is a thermoplastic which may be selectedfrom, but not limited to, the group comprising acrylonitrile butadienestyrene, polypropylene, polyethylene, polyvinylchloride, polyamide,polyester, acrylic, polyacrylic, polyacrylonitrile, polycarbonate,ethylene-vinyl acetate, ethylene vinyl alcohol, polytetrafluoroethylene,ethylene chlorotrifluoroethylene, ethylene tetrafluoroethylene, liquidcrystal polymer, polybutadiene, polychlorotrifluoroehtylene,polystyrene, polyurethane, and polyvinyl acetate.

In one aspect, the polymer is a thermoset which may be selected from,but not limited to, the group comprising vulcanised rubber, Bakelite(polyoxybenzylmethylenglycolanhydride), urea-formaldehyde foam, melamineresin, polyester resin, epoxy resin, polyimides, cyanate esters orpolycyanurates, silicone, and the like known to the skilled person.

In one aspect, the polymer is an elastomer which may be selected from,but not limited to, the group comprising polybutadiene, butadiene andacrylonitrile copolymers (NBR), natural and synthetic rubber,polyesteramide, chloropene rubbers, poly(styrene-b-butadiene)copolymers, polysiloxanes (such as Polydimethylsiloxane (PDMS)),polyisoprene, polyurethane, polychloroprene, chlorinated polyethylene,polyester/ether urethane, poly ethylene propylene, chlorosulphanatedpolyethylene, polyalkylene oxide and mixtures thereof.

In one aspect, the polymer is a biopolymer which may be selected from,but not limited to, the group comprising gelatin, lignin, cellulose,polyalkylene esters, polyvinyl alcohol, polyamide esters, polyalkyleneesters, polyanhydrides, polylactide (PLA) and its copolymers andpolyhydroxyalkanoate (PHA).

In one aspect, the polymer is a copolymer selected from, but not limitedto, the group comprising copolymers of propylene and ethylene, acetalcopolymers (Polyoxymethylenes), polymethylpentene copolymer (PMP),amorphous copolyester (PETG), acrylic and acrylate copolymers,polycarbonate (PC) copolymer, styrene block copolymers (SBCs) to includepoly(styrene-butadiene-styrene) (SBS), poly(styrene-isoprene-styrene)(SIS), poly(styrene-ethylene/butylene-styrene) (SEBS), ethylene vinylacetate (EVA) and ethylene vinyl alcohol copolymer (EVOH) amongstothers.

In one aspect, the fins are made from one continuous sheet of material,or wherein one or more of the plurality of fins are composed of two ormore different sheets of material. Preferably, one or more of theplurality of fins can be uniform or varied in composition.

In one aspect, the single sheet of material is a sheet composed of asingle material, or a laminate or composite of multiple sheets of thesame or different material.

In one aspect, the plurality of fins are applied to a heat source, suchas a solar panel, as a singular unit or a series of unit. The units canbe segmented units or a series of colinear units.

In one aspect, the air flow through the heat exchanger is by forced,natural, or passive convection.

In one aspect, the heat exchanger operates with a working fluid system.Typically, the working fluid in the working fluid system is water, oil,liquid nitrogen, or a refrigerant. Typical refrigerants arechlorofluorocarbons, hydrochlorofluorocarbons, and hydrofluorocarbons.

In one aspect, the plurality of fins further comprises a support base.Preferably the support base is mounted individually to each fin.Ideally, the support base is mounted to two or more fins.

In one aspect, the support base is opaque, transparent, or a combinationthereof.

In one aspect, the fins have a cross-sectional shape selected from atrapezoid, a sinusoid, a triangle, free-flowing, a square, a circle, apentagon, a parallelogram, a kite, a crescent, a trefoil, a chevron, across, an equiangular shape, columnar, an oblong, an oval, a teardrop, amedallion, a star, a diamond, an L-shape.

In one aspect, the plurality of fins are attached to the solar panelunit with an adhesive or by a friction fit with a frame of the solarpanel unit. In one aspect, the adhesive is a water-based pressuresensitive adhesive, a modified silicone adhesive, or an epoxy.

In one aspect, the heat exchanger further comprises a top support.

In one aspect, the heat exchanger further comprises an airflow isolationmeans across the width of the plurality of fins.

In one aspect, the heat exchanger further comprises a base plate.Preferably, the base plate is made from a metal such as aluminium,stainless steel, titanium, copper, tungsten or alloys including thesematerials. Ideally, the base plate is made from a white or transparentmaterial selected from glass, diamond, polymer, quartz, oxides andnitrides of transition metals such as aluminium nitride, aluminiumoxide, Titanium Dioxide, and the like.

In one aspect, one or more of the plurality of fins further compriseapertures, louvres, or dimples.

In one aspect, a plurality of the heat exchanger can be stacked one ontop of the other.

Preferably, each heat exchanger of the plurality of stacked heatexchangers has a different fin thickness (t_(fin)), fin height(h_(fin)), or fin length (L_(fin)), or a combination thereof. Ideally,each heat exchanger of the plurality of stacked heat exchangers is madefrom a different material.

In one aspect, the plurality of fins are applied to a heat source as asingular unit, or as a series of units. Preferably, the heat source isselected from a photovoltaic solar panel, a solar thermal collector, aPVT system, a heat pump, a radiator, an air conditioning unit, a batteryunit, an electronic device, a transformer, or a chemical reactor.

In one aspect, the heat exchanger described above can be used with aphotovoltaic solar panel, a solar thermal collector, a PVT system, aheat pump, a radiator, an air conditioning unit, a battery unit, anelectronic device, or a chemical reactor.

In one aspect, the plurality of fins are coated with a high emissivitythin film or paint.

In one aspect, there is provided a method of producing a heat exchangeras described above, the method comprising the steps of forging,extruding, stamping, punching, forming, die casting or machining theplurality of fins. In one aspect, when the fins are machined, they arestamped, punched, or formed from one or more sheets of material.

In one aspect, the fins are forged, extruded, die cast or machined froma single piece of material. In one aspect, when the fins are machined,they are stamped, punched, or formed from a single sheet of material.

In one aspect, the plurality of fins are forged, extruded, die cast ormachined individually. In one aspect, when the fins are machined, theyare stamped, punched, or formed from a sheet of material.

In one aspect, each of the plurality of fins are folded back to between1° to 90° relative to the surface of the sheet of material.

In one aspect, there is provided a photovoltaic solar panel geometrycomprising the heat exchanger described above.

In one aspect, the photovoltaic solar panel is bifacial or monofacial.

In one aspect, there is provided a back plate for a photovoltaic solarpanel which includes the heat exchanger design.

Some of the key aspects of the claimed invention is that the fins of thepanel are formed from a single sheet of material by punching the desiredshape in the material and folding the fin to an upright position. Thismethod is a scalable process. The resulting heat exchanger or heatexchanger maximises its surface area while minimising the amount ofmaterial used. The open fin structure benefits from mixing and forcedconvection due to wind. A segmented offset design enhances heat transferby a factor of 2 compared to continuous parallel fins, which has notbeen shown for PV before. The heat exchanger of the claimed inventionallows air and light directly to the back surface of the panel via thecut-out apertures which form when the fin shape is punched out from thesingle sheet of material. The material and fin design is lightweightenough to be retrofitted or attached to a panel using low cost pressuresensitive adhesive (PSA). The fins are short enough to fit within theexisting frame of standard solar panels allowing them to be retrofittedat a solar farm without dismounting the solar panel. Thus, the heatsinkof the claimed invention can be retrofitted to existing solar panels,can be used with bifacial solar panels, avails of wind-based forcedconvective cooling, and can customise heat transfer performance bystacking multiple heat exchangers in particular configurations. The heatexchanger of the claimed invention can also be used with or for solarthermal collectors, Photovoltaic thermal (PVT) systems or collectors,thermal management of electronics devices such as batteries, thermalmanagement of network hardware (5G, 6G), improving energy conversionprocesses such as in fuel cells, carbon capture systems, andthermoelectrics. The heat exchanger of the claimed invention can also beof use for improved heat transfer at low heat fluxes such as in lowtemperature radiators.

Definitions

In the specification, the term “heat sink” or “heat exchanger” should beunderstood to mean a passive device that facilitates the transfer ofthermal energy from one medium to another. For example, the heatgenerated by an electronic or a mechanical device is often transferredto a to a fluid medium via a heat exchanger, often air or a liquidcoolant, where it is dissipated away from the device, thereby allowingregulation of the device's temperature at optimal levels. The heat sinkor heat exchanger may operate using conduction, convention or radiativeheat transfer, or a combination of these mechanisms.

In the specification, the term “solar panel” or “solar photovoltaic (PV)panels or systems” are interchangeable terms that should be understoodto mean an assembly of photovoltaic cells mounted in a framework forinstallation. Photovoltaic cells use sunlight as a source of energy andgenerate direct current electricity. A collection of PV cells is calleda PV Panel, and a system of Panels is an Array. Arrays of a photovoltaicsystem supply solar electricity to electrical equipment. Solar panelscan be unifacial or monofacial (accepting light from one side only) orbifacial (accepting light from both sides).

In the specification, the term “natural convection”, “passiveconvection”, or “free convection” should be understood to mean amechanism, or type of mass and heat transport, in which the fluid motionof air is generated only by density differences in the fluid occurringdue to temperature gradients, not by any external source (like a pump,fan, suction device, etc.). The driving force for natural convection isgravity. The terms can be used interchangeably.

In the specification, the term “forced convection” should be understoodto mean a mechanism in which the fluid motion of air is generated by anexternal source such as a pump, a fan, a suction device, or wind etc.

In the specification, the term “base plate” should be understood to meana plate which supports the fins to stand in a fixed direction. The baseplate can be continuous connecting all the fins or can be separate foreach individual fin. The base plate can be made from metal such asaluminium, or transparent materials such as glass or polymer, and thelike.

In the specification, the term “solar panel mounting system” or“photovoltaic mounting systems” should be understood to mean a system ofsupport structures which allow the panel to be mounted on a pitchedroof, mounted on a flat roof, mounted on a wall. mounted on a pole,ground mounted, or mounted on floating platform.

In the specification, the term “segmented” should be understood to meanwhere a plurality of fins attached to, for example, the back of aphotovoltaic solar panel are adhered in a series of segments rather thanin a single block of fins.

In the specification, the term “segment” should be understood to mean arow of fins on a sheet of material. For example, the sheet of materialof FIG. 1(a) has 5 segments while FIG. 1(d) shows two segments.

In the specification, the term “top support” should be understood tomean a support placed on the upper peak of the plurality of fins. Thetop support may be made from the same material as the fins or adifferent material and is to provide mechanical stability.

In the specification, the term “an airflow isolation means” should beunderstood to mean a method of keeping air separate in each of thesections of fins to avoid mutual heat exchange between sections.

The term “polymer” in the specification should be understood to mean alarge molecule (macromolecule) composed of repeating structural units.These subunits are typically connected by covalent chemical bonds.Although the term “polymer” is sometimes taken to refer to plastics, itactually encompasses a large class comprising both natural and syntheticmaterials with a wide variety of properties. Such polymers may bethermoplastics, elastomers, or biopolymers.

The term “copolymer” should be understood to mean a polymer derived fromtwo (or more) monomeric species, for example a combination of any two ofthe below-mentioned polymers. An example of a copolymer, but not limitedto such, is PETG (Polyethylene Terephthalate Glycol), which is a PETmodified by copolymerization. PETG is a clear amorphous thermoplasticthat can be injection moulded or sheet extruded and has superior barrierperformance used in the container industry.

The term “thermoset” should be understood to mean materials that aremade by polymers joined together by chemical bonds, acquiring a highlycross-linked polymer structure. The highly cross-linked structureproduced by chemical bonds in thermoset materials is directlyresponsible for the high mechanical and physical strength when comparedwith thermoplastics or elastomers materials.

In the specification, the term “phase change material (PCM)” should beunderstood to be a substance which releases/absorbs sufficient energy atphase transition to provide useful heat/cooling. There are several typesof PCM available, but the there are three main types: organic (paraffinand nonparaffin), inorganic (salt hydrates and metallic alloys), andeutectic (mixture of two or more PCM components: organic, inorganic, andboth).

In the specification, the term “sheet of material” or “film” can beregarded as meaning the same, that is, a thin continuous piece ofmaterial, and can be used interchangeably. The thickness of the sheet orfilm is typically between about 0.001 mm to about 5 mm.

In the specification, the term “electronic device” should be understoodto mean a y electronic device requiring heat dissipation or activecooling including but not limited to a processor chip, an LED or LEDarray, communications hardware, batteries etc.

In the specification, the term “chemical reactor” should be understoodto mean an enclosed volume in which a chemical reaction takes place, andwhich may generate heat.

The term pressure sensitive adhesive (PSA) should be understood to meana type of non-reactive adhesive which forms a bond when pressure isapplied to bond the adhesive with a surface. No solvent, water, or heatis needed to activate the adhesive. The degree of bond is influenced bythe amount of pressure which is used to apply the adhesive to thesurface. It is used in pressure-sensitive tapes, labels, glue dots, notepads, automobile trim, and a wide variety of other products.

The invention described herein does not claim to accelerate airflow likesome of the heat exchanger designs of the prior art. The inventiondescribed herein illustrates that increasing the height of a pluralityof fins from the bottom to the top of the solar panel will help tocreate more uniform cooling. This is precisely the opposite direction oftapering as claimed in some prior art documents.

The invention described herein applies to standard solar photovoltaicpanels (PV). Standard PV generates much lower heat flux and it is notobvious that heat exchanging would work well in this situation.Furthermore, the optimum fin design in relation to spacing and heightwill be different in the case of PV than for CPV.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be more clearly understood from the followingdescription of an embodiment thereof, given by way of example only, withreference to the accompanying drawings, in which:—

FIG. 1(a)-(d) illustrates an embodiment of the invention with asegmented fin design. Fins are made from 0.5 mm thick sheet of material,aluminium for example, having a height of 2.5 cm and spaced apart by 3cm. In FIG. 1 (a) there are 23 fins spread across a 15 cm by 15 cm testpanel. In FIG. 1(b) the fins are shown on a typical 320Wp panel designedto be mounted in a portrait orientation. FIG. 1(c) shows a close-up ofthe fins adhered to back of a panel. FIG. 1(d): illustrates a basicsub-unit of the invention which is used to identify and label the keyparameters. This shows two segments which are offset by a distanceL_(off). The channel spacing in each segment is given by S, and eachsegment is separated by an interruption distance L_(int). The fin heighth_(fin) and fin length L_(fin) are defined as shown in the figure. Finthickness tin is also shown. Once the fin is cut out and folded back atan angle, an aperture is formed, allowing light to the back of the cell,with the aperture have a width W_(A) and a length L_(A). This may be thesame as the fin dimensions or larger depending on the cutting process.

FIG. 2(a)-(i) (a) and (i) illustrate isometric view of a segmented findesign made from single fins separately adhered to a panel; (b)illustrates an example of a single fin with triangular support; (c)illustrates an example of individual fins on a panel (white rectangle);(d) illustrates an example of a single fin with a rectangular base; (e)illustrates an example of fins mounted individually with a rectangularbase; (f) illustrates an example of fins with a rectangular base madeinto continuous base plate; (g) illustrates fins mounted on a separatebase plate; and (h) illustrates fins bent at the bottom to attach to abase plate.

FIG. 3(a)-(d) illustrates examples of fin materials and layerstructures. (a) is a single material fin with base; (b) is a highthermal conductivity thin fin material with a support material; (c) is ahigh thermal conductivity fin material encapsulated in a supportmaterial; and (d) is a high thermal conductivity material included asparticles in a support material.

FIG. 4(a)-(j) illustrate fin geometry alternates in profile attached toa panel (white rectangle) (a-e) shows back of panel attachments; (f-j)show both back and front of panel attachments. (a) is a singlecontinuous fin; (b) is a plurality of segmented fins; (c) is a singlefin with varying height; (d) is a plurality of segmented fin withvarying height; (e) is a plurality of segmented fins with structures toisolate airflow across each section. (f(-(j) Same designs as shows in(a)-(e) but with the heat exchanger of the claimed invention on thefront surface of the panel. The heat exchangers shown here could be madeof highly reflective or transparent materials.

FIG. 5(a)-(h) show various embodiments of the heat exchanger of theclaimed invention. FIGS. 5(a), 5(b), and 5(c) shows perspective, backand side views of a segmented design with colinear fins and foursegments; FIGS. 5(d), (e), and (f) shows the same embodiment above withfin height increasing as a function of panel position. FIG. 5(g) showsan embodiment where the heat exchanger is applied as eight separateplates to a solar panel in portrait orientation. Each plate has eightsegments and there are thirty-two segments in total. FIG. 5(h) shows thesame concept applied to a solar panel mounted in landscape orientation.The fins in this case are orientated vertically i.e. in the direction ofthe flow.

FIG. 6(a) is an IR image of a 17 cm×17 cm single cell-sized panelmounted at 45°. The left-hand side of the image is a panel with no heatexchanger, while the right-hand side of the image is a panel with a 0.5mm aluminium heat exchanger. FIG. 6(b) is a graph showing the scaling ofcell temperature with heat source power (proportional to solarirradiation). The solid line is a finite element method (FEM)simulation, while the data points are experimental measurements from thetest panel.

FIG. 7(a) shows the visible and IR images of an outdoor test using twoidentical 50 W panels. The right-hand panel is modified on its backsurface with a heat exchanger of the claimed invention. FIG. 7(b) is agraph showing the temperatures over a 2-hour period measured at the backsurface of a panel with the heat exchanger of the claimed invention. MaxΔT=3.7° C. FIG. 7(c) is a graph showing experimentally measured powercurves using the PV test instrument shown in FIG. 9(a). Max power outputis increased by 27% in this case. Background temperature was 10° C. andincident irradiance was 400 W/m².

FIG. 8 illustrates the optimum fin spacing vs panel height for differentfin temperatures calculated analytically.

FIG. 9 is a graph illustrating the solar cell temperature as a functionof fin height for different materials and thicknesses of a heatexchanger of the claimed invention.

FIG. 10 illustrates (a) a schematic of a panel in a typical ground mountat 45°; and (b) a graph illustrating the panel cell temperature under 1sun illumination (1000 W/m²) without a heat exchanger (red/top curve)and with the heat exchanger of the claimed invention (black/bottomcurve).

FIG. 11 shows steps in manufacture of the invention. Fin cross sectionis first defined and punched (1). The fins are then folded back intoposition (2). Two or more plates can be overlapped to give higher findensity (4). Adhesive such as PSA can then be applied to the base or tothe area where the exchanger will be adhered.

FIG. 12(a)-(c) shows (a) thermal images of the fins of a panel of theclaimed invention in a staggered or stacked configuration. The thermalimages show relatively uniform temperature distribution over fin lengthfor a range of different designs. FIG. 12(b) shows bar chartsillustrating the experimentally measured cell temperature drop of arange of test designs with segment number varying from 1 to 9, and finthickness decreasing from 0.5 mm to 0.2 mm. FIG. 12(c) shows thepercentage power output increase per cost of material for the same rangeof fin designs.

DETAILED DESCRIPTION OF THE DRAWINGS

The inventors propose using thermally conductive films such as metallicfilms, carbon-based films, or polymer films doped with conductiveparticles to create a novel heat exchanger. Combinations of these filmscould also be used. These materials can be manufactured on a large-scaleusing extrusion and/or roll-to-roll processing. Pyrolytic graphite film,for example, is very low density (1.9 g/cm³) and has extremely highthermal conductivity (1950 W/m/K), 9.5-times that of aluminium.Currently, it is primarily used as a heat spreader in electronicdevices. Because of its high thermal conductivity, much thinner layerscan be used as compared to aluminium which significantly reduces weightand material cost. The graphite used can be either synthetic or natural(mined from the ground). It is processed into a roll which allows forefficient transport. It can be purchased in large quantities frommanufacturers.

The heat exchanger of the claimed invention can use an origami-inspiredapproach or a punched and formed approach to create novel, high-surfacearea heat exchanger designs from the film starter material. For example,the heat exchanger can be created from a single sheet of aluminium bypunching a fin shape into the sheet of material, creating a design witha large surface area. The resulting holes from the creation of thepunched fin allows light to reach the back of a solar panelaccommodating the heat exchanger, and allows the heat exchanger of theclaimed invention to be used with bifacial solar panels. When comparedto heat exchangers formed from folding a continuous sheet of metal, thedesign of the claimed invention can achieve the same cooling using lessmaterial as the back of the solar panel is still used as an effectivecooling surface. This heat exchanger can be attached directly to theback sheet of a solar panel or attached to a photovoltaic solar panelframe as shown in FIG. 1(b). FIG. 1(b) shows the fin orientation whenthe panel is intended to be mounted in a portrait orientation. FIG. 1(c)shows the case when the panel is intended to be mounted in a landscapeorientation. In FIG. 1 (d), the specifics of the design of the claimedinvention are shown on a basic subunit. The key distances which definethe invention are labelled. This includes an offset distance (L_(off)),a channel spacing (S), an interruption distance L_(int), a fin heighth_(fin), a fin length L_(fin), and a fin thickness t_(fin). Once the finis cut out and folded back, an aperture remains with a width W_(A) and alength L_(A), allowing light into the back of the cell. This may be thesame as the fin dimensions or larger depending on the cutting process.

The heat exchanger can be constructed from individual fins which areassembled as shown in FIG. 2(a). This consists of individually mountedfins as shown in FIG. 2(b) mounted as shown in FIG. 2(c). In this case,a triangular base mount is used. This may attach the fin directly to theback of the panel or to a baseplate. In FIG. 2(d) an alternativerectangular base mount is shown. They may be mounted separately as shownin FIG. 2(e) or combined into a single unit before application, such asin FIG. 2(f). Alternatively, the fins may be attached to a singlebaseplate as shown in FIG. 2(g). The fins may be folded to attach to theback of the panel, or the baseplate as shown in FIG. 2(h). These basemounts and baseplates can be made from the same material as the fin orfrom a different material. They can be transparent or opaque and madefrom metal, polymer, or glass, or a combination of these. They may bematched to the thermal expansion coefficient of the backplate, solarglass or other photovoltaic solar panel material.

The fins may be made from a single high thermal conductivity material asshown in FIG. 3(a) or may be made from a high thermal conductivitymaterial adhered to a supporting material as shown in FIG. 3(b). Theymay be made from a continuous high thermal conductivity materialencapsulated in a supporting material, as shown in FIG. 3(c), or adiscontinuous high thermal conductivity material dispersed in asupporting material, as shown in FIG. 3(d).

In one embodiment, the heat exchanger structure can be created from asingle film or material, or from multiple sections. These films may havethe structures described in FIG. 3 . By creating bends and folds in thedesign, different heat exchangers can be created by periodicallyadhering the film to the back of the panel or the baseplate. The thermalresistance of the heat exchanger can be tuned to match the solar paneldesign by choosing a material with a particular thermal conductivity κ,a film thickness t, a height of the film h, and a periodicity λ.Further, by using fins that are thin, these may be flexible andfree-moving. For example, when the material used is aluminium orgraphite, fins having a thickness of about 0.1 mm will result inflexible and free-moving fins. Free-moving structures have the advantageof moving with the wind, which would enhance heat transfer throughforced convection and turbulence. The heat exchangers of the claimedinvention do not need to be periodic or ordered. They may havesinusoidal, triangular, undulating, square, rectangular or fractal crosssections. When they are periodic, they can have multiple periodicitiesor vary depending on the position the heat exchanger of the claimedinvention takes on the panel.

Side views of embodiments of the invention are shown in FIGS. 4(a)-(j).The fin structures may be continuous along the entire panel length orapplied in sections as shown in FIG. 4(a) and FIG. 4(b), respectively.Examples are shown with 3-4 sections, however there may be any number ofsections as the user sees fit. The fin height may vary as a function ofpanel position. An example of a linear variation is shown in FIG. 4(c),and in the segmented design in FIG. 4(d). An additional structure couldbe used to separate airflow from each of the sections, as indicated bythe black line in FIG. 4(e). For some panels, such as bifacial panels,transparent base plates and fins, or highly reflective fins, aretypically used. It would be possible to use these heat exchangers on thefront surface of the panel also. The same concepts are shown both onfront and back of panel in FIG. 4(f)-(j).

Photovoltaic solar panels are mounted at an angle to optimise solarirradiation. Shallow angles may cause issues for natural convection,with air getting trapped beneath the panel. The design may requiremodification of the top and bottom parts of the frame holding the panelto allow air to flow across the heatsink surface. The heatsinks could besegmented, or the length of the heat exchanger could be varied dependingon position on the panel to optimise natural convection heat transfer,and to ensure uniform cooling. The heatsinks could be mounted as stripswith gaps between these to allow airflow to move through. The heatexchanger may be long enough to protrude from the back of the panelsurface, or it may be short enough to be completely hidden by the panelframe. Full back panel views of segmented fins are shown in FIG. 5 .Simple parallel rectangular fins are shown. These fins may be made fromany of the materials or layer structures outlined in FIG. 3 . They maybe constructed using the punched technique outlined in FIG. 2 or adheredindividually as outlined in FIG. 4 . They may have any number ofdifferent types of cross sections other than rectangular. FIG. 5(a)-(c)shows isometric, back and side views of an example of a 320Wp solarpanel with simple rectangular fins. FIG. 5(d)-(f) shows isometric, backand side views of a segmented design with tapered fins. A simple linear,tapered design is shown, however other tapered designs could be used. Insegmented designs, sections may have different fin height, periodicityand thickness. Sections may be made of different materials. Sections maybe offset to disrupt airflow between each segment.

Sections may be made of different materials. Sections may be offset todisrupt airflow between each segment. Good adhesion between the heatexchanger and the photovoltaic solar panel and the fin structure andbase are very important to ensure good thermal contact. There areseveral commercially available glues and epoxies that can be used suchas water-based pressure sensitive adhesive (PSA) or modified siliconeadhesive. For PSAs an elastomer functions as the primary base material,which can be natural rubber, vinyl ethers, acrylics, butyl rubber,styrene block copolymers, silicones and nitriles. Modified siliconesconsist of polyether backbone and silane terminal functionality. Theycan be prepared from high molecular weight polypropylene oxide, endcapped with allyl groups, followed by hydrolysation to produce apolyether end-capped with methyldimethoxysilane groups. The heatsink maybe attached without using glue, just by applying pressure against theframe. Bars could be used to evenly apply the pressure. An alternativewould be to mechanically fix the heat exchanger to the backplate usingvarious securing means such as a nail, a screw, a tack, snap-fitconfiguration, adhesive, and the like. A combination of both techniquescould be used. The contact area should be controlled in order to tunethe thermal resistance of the heat exchanger and ensure uniform cooling.

To demonstrate the performance of the heat exchanger of the claimedinvention, the inventors created a test rig where heater pads wereinserted in a standard solar panel geometry, which allowed precisecontrol of the heat source while monitoring cell temperature, surfaceglass temperature, and the heat flux through the back surface of thepanel. FIG. 6(a) shows IR thermal images of the front of the test bed.The panel on the left has no heat exchanger, whereas the panel on theright has an aluminium heat exchanger with a fin thickness of 0.5 mm. Totest performance under different conditions, the current in the heaterpad is controlled such that the heat source density changes from 100W/m² to 800 W/m². FIG. 6(b) shows the resulting solar cell temperaturemeasured experimentally (data points) and predicted using numericalsimulations (solid line).

The inventors also compared the performance of two identicalmonocrystalline 50 W solar panels with and without the heat exchanger ofthe claimed invention. The panels were placed outdoors in realisticweather conditions at the beginning of March in Ireland (see FIG.7(a)-(c)). Maximum solar irradiance was measured at 600 W/m² and thebackground temperature was 10° C. The backside of the panel with notechnology reached 30° C., whereas the backside temperature with thetechnology remained below 25° C. Even with a small change intemperature, a significant increase of 27% in output power from thepanel with the heat exchanger of the claimed invention was observed.

The inventors performed extensive analytical and numerical studies tooptimise the design. FIG. 8 illustrates the relationship between theoptimum fin spacing and the panel height at various temperatures,calculated using analytical theory. The optimum spacing depends onaspect ratio and the expected fin operating temperature.

The optimum fin height and thickness are calculated using numerical FEMsimulations. In FIG. 9 , it is shown that for the aluminium foil (athickness of 0.05 mm) there is a reduced benefit in increasing the finheight past 50 mm. This is because the thermal resistance is large andthe thermal gradient along the fin height is significant. Increasing theheight of the fin beyond this has minimal effect because the temperaturedifference between the fin and the air is too low to exchange areasonable amount of heat. For the thicker aluminium sheet (0.5 mm)there are benefits out to 10 cm, however this will add additional costand weight to the device.

FIG. 10 shows simulated results for a full-scale panel demonstrating a24° C. temperature drop with the applied technology. This wouldcorrespond to ˜12% increase in output efficiency and could significantlyincrease panel lifetime.

FIG. 11 shows a proposed manufacturing process for the heat exchanger ofthe invention. The cross-section of the fin is first defined usingpunching, cutting, laser scribing or similar mechanical processes. Thefin is then released from the sheet by folding the fin back to between1° and 90° relative to the sheet surface. Individual plates can beoverlapped to increase the fin density (see FIG. 12(a) “stacked”). Whenstacking individual plates one on top of the other, the plurality offins of a second plate fit through the apertures created by theplurality of fins of a first plate. The stacked plates can be movedrelative to each other to create a specific spacing between the fins ofthose plates as desired. In general, the plurality of fins of the firstplate are placed in the centre of the apertures of the second plate.This effectively decreases the spacing of the fins on the stacked platesby half and provides an improved fin density regime for cooling. Anadhesive is applied to the back of the heat exchanger to permit the userto adhere the heat exchanger to a device. The process of using a singlesheet of material uses much less material than folding a single sheetand opens apertures which allow light to the back of the panel.

FIG. 12(a) shows a thermal image of a specific design, and the stackedversion of that design with higher fin density. The relatively uniformfin temperature shows that they are acting with high fin efficiency andwell contacted to the heat source. FIG. 12(b) shows the experimentallymeasured temperature reduction at cell level for different numbers ofsegments from 1 to 9 and thicknesses ranging from 0.5 mm to 0.2 mm. Thisshows that there is limited change in the temperature performance whenreducing thickness to 0.2 mm. FIG. 12(c) shows that the cost per % poweroutput improvement decreases with thinner fin thickness. This shows anadvantage to going to thinner fins.

Materials and Methods Solar Panel Construction

A typical layout of a photovoltaic solar panel is a layer of glass, afirst encapsulant layer, a solar cell, a second encapsulant layer, and aback sheet. The glass is low iron tempered glass and usually between2.8-4 mm thick. It provides the main structural support for the solarcells, which are extremely thin and brittle. The encapsulant is usuallya form of ethylene-vinyl acetate (EVA) optimized to withstand prolongedUV exposure. The back sheet can be made of polyethylene terephthalate(PET), polyvinylidene fluoride (PVDF), or propriety materials such asDuPont™ Tedlar® (a polyvinyl fluoride film). These materials mustprotect the cells from moisture ingress and temperature cycling.

Heat Exchanger Materials

The proposed heat exchanger can be made from any material with highthermal conductivity (>50 W/m/K). In particular, the inventors havedemonstrated the heat exchanger of the claimed invention using aluminiumand expanded graphite. The high thermal conductivity material may besupported or encapsulated by a low thermal conductivity material ingeometries as depicted in FIG. 3 . Metals including but not limited toaluminium, copper, stainless steel, titanium and alloys containing theseelements. Carbon-based materials including but not limited to graphite,pyrolytic graphite, expanded graphite, diamond, carbon filler, carbonnanotubes, graphene are of particular interest due to low density, highthermal conductivity and high IR emissivity. Other high thermalconductivity materials such as aluminium nitride, silicon nitride andboron nitride are of interest.

Heat Exchanger Testing

To reproduce the effects of heating due to solar irradiation of a solarpanel in a quantitative and reproducible fashion, the inventors deviseda simple rig with a silicone heating mat in place of a silicon solarcell. A glass front panel and a polycarbonate back panel were cut toarea 17 cm×17 cm. The glass was 2.8 mm thick and the PC panel was 1.5 mmthick. A heating mat was used with an input voltage of 12V, and maximumpower dissipation of 15 W. This permitted the inventors to get up to 800W/m² as a heat source density, which is enough to represent solar panelsunder standard test conditions. A thermal image of the front surface(glass) is shown of the device without and with the heat exchanger onleft and right-hand sides respectively in FIG. 6(a). The image is takenwith a heat source density of 800 W/m². The current was controlled tosweep the heat source density from 100 W/m² to 800 W/m² and the celltemperature was monitored with and embedded thermocouple for the caseswith and without the heat exchanger. The results are shown in FIG. 6(b).The experimental measurements are shown as data points, whereas thesolid lines represent the prediction of numerical models performed usingthe 3D finite element method. In extreme environments, panels couldexperience peak heat source densities of 1920 W/m². A higher powerheating mat is required to simulate these conditions.

As a further demonstration a standard 50 W photovoltaic solar panel wasfitted with a heat exchanger made using a 0.5 mm aluminium sheet.Individual fins were adhered to the back of the solar panel without theuse of a back plate to reduce cost. FIG. 7(a) shows visible and thermalimages of the device of the claimed invention in outdoor conditionsunder 600 W/m² solar irradiance. The panel on the right is fitted withan aluminium heat exchanger of the claimed invention with 0.5 mmthickness. FIG. 7(b) shows the temperature recorded at the back of thepanel without (black) and with (red) the heat exchanger of the claimedinvention with background temperature (blue).

FIG. 7(c) shows the power output curve measured using industry standardinstrumentation with (black) and without (red) the heat exchanger. Thisdemonstrated a 27% increase in output power under the conditions given.

Optimum Design

The important parameters for the natural convection heat exchangerdesign are the fin height h_(fin), the fin thickness t_(fin) and the finspacing S. The fins define air channels of thickness (fin spacing) S,and the fluid properties, temperature difference and aspect ratio of theproblem determine the optimum fin spacing S_(opt). In natural convectionthere is no external driving force and one must rely on buoyancy todrive the airflow. As such, the balance between buoyancy force andviscous drag is critical and determines the steady state fluid flow.There are several dimensionless parameters which can be used tocharacterize different regimes of fluid flow. The optimum spacingS_(opt) can be found analytically for flat plate geometry and is wellknown from the academic literature (Thermally Optimum Spacing ofVertical, Natural Convection Cooled, Parallel Plates, A. Bar-Choen, andW. M. Rohsenow, Transactions of ASME, 116/Vol. 106, FEBRUARY 1984).

In one embodiment of the present invention, an optimum spacing of 0.8 cmfor the 17 cm testbed was preferred, increasing to 1.4 cm for a standard320 W panel of height 1.5 m. A simple fin-type heat exchanger was chosento allow simple analytical expression to understand scaling. Fin length,spacing and thickness could be changed as a function of position on aphotovoltaic solar panel in order to ensure uniform temperature of thecells in the photovoltaic solar panel, if this is deemed important.

The optimum fin spacing derived above assumes the fins are uniformtemperature and are of negligible thickness, so they effectively havevery high thermal conductivity. Realistic fin performance will depend onits thermal resistance, and there will be an optimum thickness andlength. The optimum fin thickness and length for a specific fin materialcan be determined using finite element method numerical simulations.These simulations performed by the inventors include heat transfer dueto conduction, convection and radiation and a full analysis of the fluidflow.

The optimum fin length h_(fin) depends on the temperature difference,but also the fin thickness and the material thermal conductivity. Usinga high thermal conductivity material or thicker fin allows similarperformance to be achieved at a shorter fin length. The inventors usedtwo thicknesses of 0.05 mm and 0.5 mm to demonstrate this for fins madefrom aluminium and graphite foil, a synthetic high thermal conductivematerial, as shown in FIG. 9 . The thinner sample of 0.05 mm isrepresentative of aluminium foil, which has a thickness in this range.The solar panel surface temperature is shown to decrease appreciably upto 50 mm, after which there are little gains. The thicker fin (0.5 mm)represents thin sheet metal which is more rigid. This shows asignificantly lower temperature and gains are continued to be observedout to 100 mm. In this case, the cost and weight of the aluminium becomea factor and the optimum length will need to be decided as a trade-offbetween cost, weight and performance.

The use of a synthetic graphite foil with a thermal conductivity of 1500W/m/K is almost 8-times more thermally conductive than aluminium and hasa lower density. The simulations show a slight improvement with the 0.5mm thickness case as compared to 0.5 mm of aluminium. However, the moreexciting result is that the 0.05 mm graphite film fin still outperformsthe 0.5 mm aluminium fin. This graphite film fin is likely to be moreexpensive than aluminium, however it seems that one could usesignificantly less material, which would allow a user to save on costand weight.

Although many different cooling technologies have been proposed in thepast, they have not proven economically viable for large scalephotovoltaic solar panel farms. The heat exchanger of the claimedinvention can be retrofitted to existing solar panels in order toincrease electricity output and prolong the lifetime of the solar panelsthemselves. The heat exchanger of the claimed invention can be addedpost-production to existing back sheet solar panels, or the heatexchanger itself could serve the function of the back sheet and beintegrated at the panel manufacturing stage. The cost of photovoltaicsolar panels has decreased by a factor of 10 in the last 5 years. Insome arid regions, with high solar irradiance, such as parts of India,solar power generation has become cheaper than fossil fuels. The use ofthe heat exchanger of the claimed invention could lower the cost ofproduction even further allowing solar panel farms globally to competewith other renewable and non-renewable power generation technologies.

In the specification the terms “comprise, comprises, comprised andcomprising” or any variation thereof and the terms “include, includes,included and including” or any variation thereof are considered to betotally interchangeable and they should all be afforded the widestpossible interpretation and vice versa.

The invention is not limited to the embodiments hereinbefore describedbut may be varied in both construction and detail.

1. A heat exchanger comprising a plurality of fins spaced apart fromeach other, the plurality of fins having a predetermined length(L_(fin)), thickness (t_(fin)) and height (h_(fin)); wherein theplurality of fins are formed from a single sheet of material, andwherein where each fin of the plurality of fins are formed, an aperturehaving a predetermined width (W_(A)) and a predetermined length (L_(A))is generated in the single sheet of material separating each fin of theplurality of fins.
 2. The heat exchanger according to claim 1, whereinthe plurality of fins have on open configuration through the heatexchanger.
 3. The heat exchanger according to any one of claim 1 or 2,wherein the plurality of fins are segmented into distinct sections. 4.The heat exchanger according to any of the preceding claims, wherein theplurality of fins are arranged in a colinear or an offset mannerrelative to each other.
 5. The heat exchanger according to any one ofthe preceding claims, wherein fin spacing, fin height or fin thicknesschange as a function of position on the single sheet of material.
 6. Theheat exchanger according to any one of the preceding claims, wherein theoptimum fin spacing (S) is between about 1 mm and about 50 mm relativeto each other.
 7. The heat exchanger according to any one of thepreceding claims, wherein the fin thickness (t_(fin)) is between about0.001 mm to about 5 mm; the fin height (h_(fin)) is optionally betweenabout 0.1 cm to about 10 cm; and the fin length (L_(fin)) is optionallybetween about 1 mm to about 1500 mm.
 8. The heat exchanger according toany one of the preceding claims, wherein the fins are composed ofthermally conductive sheets or films of material selected from the groupcomprising a metallic film, a carbon-based film, or polymer films dopedwith conductive particles or a combination thereof.
 9. The heatexchanger according to claim 8, wherein the metallic films are selectedfrom films comprising aluminium, copper, stainless steel, tungsten,titanium, or combinations thereof.
 10. The heat exchanger according toclaim 9, wherein the carbon-based films are selected from filmscomprising graphite, pyrolytic graphite, synthetic graphite, graphene,carbon nanotubes, expanded graphite, graphite composites, carbon black,diamond, or combinations thereof.
 11. The heat exchanger according toclaim 9 or claim 10, wherein the conductive particles in the polymerfilms are selected from a diamond, carbon, transition metal nitridessuch as AlN, transition metal oxides such as Al₂O₃, ceramics orcombinations thereof.
 12. The heat exchanger according to any one of thepreceding claims, wherein the plurality of fins are flexible.
 13. Theheat exchanger according to any one of the preceding claims, wherein theplurality of fins are coated with an epoxy or polymer.
 14. The heatexchanger according to claim 13 wherein the coating is selected from anelastomer, a phase change material, a thermoplastic, a copolymer or acombination thereof.
 15. The heat exchanger according to any one of thepreceding claims, wherein the single sheet of material is a sheetcomposed of a single material, or a laminate or composite of multiplesheets of the same or different material.
 16. A heat exchangercomprising a plurality of fins spaced apart from each other and having apredetermined length (L_(fin)), thickness (t_(fin)) and height(h_(fin)); and wherein each fin of the plurality of fins has apredetermined shape and is attached individually to a plate.
 17. Theheat exchanger according to claim 16, wherein the plurality of fins arecomposed of the same material, a composite of the same material, or acomposite of different material.
 18. The heat exchanger according to anyone of the preceding claims, wherein air flow through the heat exchangeris by forced, natural, or passive convection.
 19. The heat exchangeraccording to any one of the preceding claims, wherein the plurality offins further comprises a support base.
 20. The heat exchanger accordingto claim 19, wherein the support base is mounted individually to eachfin.
 21. The heat exchanger according to claim 19 or 20, wherein thesupport base is opaque, transparent, or a combination thereof.
 22. Theheat exchanger according to any one of the preceding claims, wherein thefins have a cross-sectional shape selected from a trapezoid, a sinusoid,a triangle, free-flowing, a square, a circle, a pentagon, aparallelogram, a kite, a crescent, a trefoil, a chevron, a cross, anequiangular shape, columnar, an oblong, an oval, a teardrop, amedallion, a star, a diamond, an L-shape.
 23. The heat exchangeraccording to any one of the preceding claims, further comprising anairflow isolation means across the width of the plurality of fins. 24.The heat exchanger according to any one of the preceding claims, furthercomprising a base plate.
 25. The heat exchanger according to claim 24,wherein the base plate is made from a metal selected from aluminium,stainless steel, titanium, copper, tungsten or alloys thereof.
 26. Theheat exchanger according to claim 24, wherein the base plate is madefrom a white or a transparent material.
 27. The heat exchanger accordingto claim 26, wherein the white or transparent material is selected fromglass, diamond, polymer, quartz, oxides and nitrides of transitionmetals such as aluminium nitride, aluminium oxide, Titanium Dioxide, andthe like.
 28. The heat exchanger according to any of the precedingclaims, wherein one or more of the plurality of fins further compriseapertures, louvres, or dimples.
 29. The heat exchanger according to anyone of the preceding claims, wherein a plurality of the heat exchangercan be stacked one on top of the other.
 30. The heat exchanger accordingto claim 29, wherein each heat exchanger of the plurality of stackedheat exchangers has a different fin thickness (t_(fin)), fin height(h_(fin)), or fin length (L_(fin)), or a combination thereof.
 31. Theheat exchanger according to claim 29 or claim 30, wherein each heatexchanger of the plurality of stacked heat exchangers is made from adifferent material.
 32. The heat exchanger according to any one of thepreceding claims, wherein the plurality of fins are applied to a heatsource as a singular unit, or as a series of units.
 33. The heatexchanger according to claim 32, wherein the heat source is selectedfrom a photovoltaic solar panel, a solar thermal collector, a PVTsystem, a heat pump, a radiator, an air conditioning unit, a batteryunit, an electronic device, a transformer, or a chemical reactor. 34.The heat exchanger of any one of the preceding claims for use with aphotovoltaic solar panel, a solar thermal collector, a PVT system, aheat pump, a radiator, an air conditioning unit, a battery unit, anelectronic device, or a chemical reactor.
 35. A heat exchanger for usewith a photovoltaic solar panel unit having a top and a bottom, the heatexchanger comprising a plurality of fins spaced apart from each otherand each fin of the plurality of fins having a predetermined length(L_(fin)), thickness (t_(fin)) and height (h_(fin)), wherein theplurality of fins are formed from a single sheet of material and whereinan aperture having a predetermined width (W_(A)) and a predeterminedlength (L_(A)) is generated in the single sheet of material between eachof the plurality of fins.
 36. The heat exchanger according to any one ofthe preceding claims, wherein the plurality of fins are coated with ahigh emissivity thin film or paint.
 37. A photovoltaic solar panelgeometry comprising the heat exchanger of claim 1; wherein thephotovoltaic solar panel is either bifacial or monofacial.
 38. A methodfor making the heat exchanger of claim 1, the method comprising thesteps of forging, extruding, stamping, punching, forming, die casting ormachining the plurality of fins from the single sheet of material,folding back one or more of the plurality of fins from the surface ofthe sheet of material, wherein said folding back of the fin generates anaperture between each fin of the plurality of fins in the single sheetof material.
 39. The method of claim 38, wherein each of the pluralityof fins are folded back to between 1° to 90° relative to the surface ofthe sheet of material.